Feed-water heater for boilers, particularly adapted for locomotives



y 1940- P. CROSTI 2,200,492

FEED-WATER HEATER FOR BOILERS, PARTICULARLY ADAPTED FOR LOCOMOTIVES Filed May 11, 1938 a: is 5 as is |NVENTOR= PIETRO -CRO5TI I JWM e jf AT TORNEYS Patented May 14, 1940 UNITED STATES- FEED-WATER. HEATER FOR BOILERS, PAR- TICULAELY ADAPTED FOR LOCOMOTIVES Pietro Crosti, Milan, Italy Application May 11, 1938, .Serial No. 207,210

. In Italy June 1, 1937 3 Claims.

Experiments on steam locomotives provided with feed-Water heaters, have made clear that one of the causes of high efiiciency depends on the efiiciency of any arrangement used for obtaining the heat exchange through a separating wall between two fiuids moving in opposite directions in counterflow.

The reduction of frictional resistances plays an important part in the process as it represents a net gain in power obtained by reducing the work involved for producing the draught of the combustion gases, the latter being secured by the greatest possible amount of exhaust steam, brought, at the same time, to a higher specific volume by heat units otherwise lost.

In the following specification forming the description of the invention, an arrangement is described by which the highest thermal efliciency and the greatest saving in coal are obtained With a very simple construction and easy maintenance.

Figure 1 of the accompanying drawing shows one of the simplest constructions of the feedwater heater made according to the invention.

Figure 2 shows one of the ways in which the feed-water heater may be applied to a boiler by being arranged under the same.

Figure 3 shows one or more feed-water heaters placed beside of the boiler.

Figure 4 shows a locomotive provided with a 30 feed water heater mounted on a truck, separate from the boiler.

The feed-water heater according to the present invention and illustrated in Figure 1, comprises a cylindrical body I containing a set of flue tubes 2 placed within the same and limited by tubeplates 3 and 4, cased in externally by shrouds Ill and II.

The combustion gases arriving in chamber 5 follow the fines 2, pass into smoke-box chamber 6 and issue from stack 7.

The centre line of this heater is arranged as steeply inclined as possible with respect to the horizontal and with regard to the space afforded and in such a Way as to keep the end 5 highest through which the combustion gas enters. The feed water, which in this heater is heated to a proper temperature, enters the body I from pipe 8 and flows out from the pipe 9.

The shroud l0 jackets the cylindrical body along its whole length and protects it from heat losses to the outside.

The inner shroud I I, inside the shroud ID, in turn jackets the feed-Water heater cylinder I from the lowest end, comprising the smoke-box 6, 55 and rises towards the-tube-plate 3 for such a length as considered convenient for reasons which will be disclosed hereafter.

Such an arrangement secures the following important advantages both of thermal and functional character.

The slope given to the cylindrical body I, obtains a feed-water exit at 9 at a much higher level than the water entrance at 8, so that the Water, on entering the heater and dropping across the flues into the lower part of the cylindrical body, just under the entrance 8, is caused to rise, as soon as its increasing temperature diminishes its specific gravity, towards the exit 9 following the slope of the lines along a path which is almost parallel to the same and consequently in counter-flow to the combustion gases which arrive from chamber 5 and pass into chamber 6.

The water strata having the same temperature follows, approximately, the lines of equal temperature l2 (isotherms) almost at right angles with the direction of the water-flow.

As the speed of flow of the water between the entrance at 8 and the exit at 9 may be kept very low, the salts contained in the water, with the exception of chlorides and a few more insoluble salts, precipitate slowly and settle as mud in the lower part of the cylinder l. Due to the steep slope provided, said mud will gather near the tube plate 4 and may be readily removed during the usual cleaning operation through the mud cook or door l3 placed in a convenient position.

The upward slope of the flues, inclined in the same direction as the water flow, as already shown, is an obstacle tothe settling of air bubbles along the upper sides of the fiues. This fact is very important inasmuch as experience has shown that the air bubbles'which escape from the water during its heating, adhere and usually settle for a long time along the upper part of the flues, causing a quick oxidation and corrosion of the same to such a point as to result in perforations It is clear that due to the fiues sloping, the air bubbles cannot find any condition of equilibrium and as soon as they grow to a certain size, leave the walls of the lines more easily, thus providing a regular and beneficial turbulence of the liquid which is being heated.

Another advantage of the sloping lines is that any solid materials, usually dropped by the flue gases within the fines, sink moreeasily and flow towards the smoke-box 6, due to the concomitant action of the gas draught and of gravity. Such material deposits may be removed from the smoke-box 6, through an aperture M as is usually done in similar cases.

As the distribution of isothermal surfaces of the Water in the cylindrical container, during regular operation, establishes points at which the shroud l is at a temperature not far from C. the extension of shroud H may be limited to such points, said shroud having the purpose of forming a steam-jacket in which the exhaust steam flows of the main engine or of such auxiliaries as may be at hand,v allowing also the flow of other fluids of no less than 100 C. temperature, whose heat units may also be utilized.

It is clear that the shroud l l in the portion between plate 4 and its end towards plate 3 forms with the cylinder body I, a water-heater capable of transmitting the heat units of the enveloping warm fluid to the water contained in the cylindrical body I.

In the particular case of the present invention, steam or such other fluids which have to be used find access to the shroud H from the opening l5 and flow out of aperture It, as they have entered, or else are mixed with such other fluids as may condense from them. Aperture I6 acts as a blast nozzle, and may be replaced by any other more convenient aperture through which the heating fluids flow out, after having been compelled to travel through the shroud ll so as to obtain the most efiicient heat exchange between the combustion gases and the feed water.

The shroud H envelopes the smoke-box 6 of the stack also, and it thus becomes possible to extract further heat units fromthe combustion gases for heating up the exhaust steam during its passage through such a portion of the shroud, thus obtaining both advantages of cooling the combustion gases, which will also diminish in volume and of superheating the steam, which, on the contrary, will increase its volume.

Thus, the work evolved in producing the draught of the combustion gases is reduced and the potential energy in the exhaust steam is increased.

As the shroud ll forms a single container enclosing both the smoke-box, where the heat exchange occurs between the combustion gases and the steam, and part of the cylindrical body of the feed-water heater, where the heat exchange instead takes place from steam to water, nothing prevents the transference of further heat directly to the water from the combustion gases, by convection or any other convenient motion imposed on the fluid in the heating jacket.

The heater may be coupled to the boiler as shown for instance in Figure 2, that is, placed under the boiler ll. The combustion gases flow from the smoke-box l8 of the boiler to chamber 5 of the heater I through the duct l9, beginning at the aperture 20 opening at the top part of the smoke-box l8, so as to allow the solid particles carried along by the gases from the furnace 23, to settle in the less disturbed part 21 of said smoke-box.

After having gone through the feed water heater the combustion gases exhaust into the atmosphere through the stack 22. Conduit I9 and stack 22 are of course placed beside of the boiler 11 and may be doubled and placed symmetrically on each side of the boiler ll when this is found convenient for heat saving or aesthetic purposes.

When the size of the heater or any other reason prevents its being placed under the boiler, as stated above, the heater may be placed alongside the boiler as shown in Figure 3, in which like numbers refer to like connecting parts. The feed-water heaters I may be doubled and placed on each side of the boiler, when conditions make it desirable.

Both the arrangements in Figures 2 and 3 maintain all the advantages previously stated.

It should also be noted that the stack 22 or the double stacks, which are placed near the engine-drivers cab, allow a discharge of smoke in such a place as not to interfere with visibility of signals.

The said arrangements are particularly convenient in those cases in which the locomotive is built as a single power-unit, capable of carrying the weight of both the boiler and the feed water heater or heaters.

In case, instead, the locomotive has to develop a very high tractive efiort, or that the driving or carrying wheels must not be loaded over a certain limit load, and therefore are unable to carry the whole load of the boiler, the feed water heater and other members required for its operation, the heater may be arranged, as shown in Figure 4 on a second truck 24 carried on a convenient number of wheels 25 which are either no driving wheels or are only partially driven. On this second truck the feed water heater is placed with the correct slope and its highest part ends with a smoke-box 5 turned towards smoke-box l8 of boiler I! from which flow the combustion gases. At the other end of the truck the smoke-box 6 is located and into which the combustion gases enter after passing through the flues 2 and before being exhausted into the atmosphere through the stack 1.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

l. A feed-water heater for steam boilers, formed by a cylinder containing a set of flues for the combustion gases, in which said cylinder with its flues so slopes appreciably with regard to the horizontal, that the part where combustion gases enter is placed much higher than the place at which they leave, while the entrance for the feed water is placed at the lowest portion of the cylinder at the opposite end of the same cylinder with regard to the feed-water exit, so that both the relative and absolute flow of the gases and of the water to be heated help all the phenomena due to counter-flow heat exchange and to the motions brought about by the variations of specific gravity of both fluids, and in which the outside surface of the cylindrical body is jacketed by two shrouds, one extending the whole length of said body, the other, placed inside the first, extending only from the end of said cylindrical body which is at the lowest temperature, upwardly to that part of said body in which the water enclosed and being preheated has not risen above the temperature of the fluid flowing in this second shroud, so as to obtain, with the first jacket, a protection against heat dispersion, and with the second jacket the utilization, in favour of the feed water being heated, of any heat units which the fluid circulating into said jacket might possess and of those which said fluid might take from the combustion gases.

2. A feed-water heater according to claim 1 which is arranged under or alongside a boiler which delivers to said heater its combustion gases and indirectly, wholly or partially, any other fluids whose heat-units are to be utilized for the heating of the feed-Water, the whole being carried on a single frame forming the locomotive carriage.

3. A feed-water heater according to claim 1 which is placed on a carriage carried by driving or non-driving wheels separate from the carriage of the boiler provided with the furnace, but forming with the latter a single locomotive with a single or a double driving unit.

PIETRO CROSTI. 

